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1.
R. D. Maksimov S. Gaidukovs M. Kalnins J. Zicans E. Plume 《Mechanics of Composite Materials》2006,42(1):45-54
The preparation of a polymer nanocomposite by compounding an aqueous polymer emulsion with an aqueous dispersion of montmorillonite
clay is described. A styrene-acrylate copolymer emulsion and a purified native montmorillonite clay from Latvian deposits
are used. An X-ray diffraction analysis and differential scanning calorimetric thermograms are shown. Data on the influence
of montmorillonite concentration on the tensile stress-strain diagram, elasticity, yield stress, breaking stress, and ultimate
elongation of the processed nanocomposite material are obtained.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 61–74, January–February, 2006. 相似文献
2.
R. D. Maksimov S. Gaidukov J. Zicans J. Jansons 《Mechanics of Composite Materials》2008,44(5):505-514
Results of an investigation into the kinetics of moisture sorption by an unfilled styrene-acrylate copolymer and a nanocomposite
containing unmodified montmorillonite clay are reported. The sorption tests were performed at 25°C and different levels of
the relative humidity of air up to 80%. The moisture diffusivity was calculated using Fick's equation for one-dimensional
diffusion. Data on the influence of montmorillonite concentration on the coefficients of diffusion, solubility, and permeability
are obtained. The experimental values of the permeability coefficient are compared with those calculated by using a model
taking into account the increased path of a diffusing water molecule caused by the shielding effect of plate like filler particles.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 5, pp. 723–736, September–October, 2008. 相似文献
3.
R. D. Maksimov S. Gaidukovs J. Zicans M. Kalnins E. Plume V. Spacek P. Sviglerova 《Mechanics of Composite Materials》2006,42(3):263-272
The preparation of polymer nanocomposites by mixing a solution of a styrene-acrylate copolymer with a suspension of organically
modified montmorillonite in dimethyl formamide is described. Seven different compositions with organomontmorillonite content
from 0 to 7 wt.% were prepared and tested. Results of their X-ray diffraction analysis are presented. Data on the influence
of organomontmorillonite content on the tensile stress-strain curves, elastic modulus, strength, and ultimate elongation of
the nanocomposites are obtained. The concentration dependences of elastic properties of materials with differently oriented
platelike nanoparticles is analyzed by using an algorithm elaborated for stepwise calculations of elastic constants with account
of the features of structural hierarchy of intercalated and exfoliated nanocomposites.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 375–388, May–June, 2006. 相似文献
4.
R. D. Maksimov S. Gaidukovs J. Zicans M. Kalnins E. Plume V. Spacek P. Sviglerova 《Mechanics of Composite Materials》2006,42(4):353-362
The results of an investigation into the barrier and thermal properties of polymer nanocomposites prepared by blending a styrene-acrylate
copolymer solution with a suspension of organically modified montmorillonite are presented. The influence of organomontmorillonite
content on the barrier properties of the nanocomposite is investigated with the example of water vapor permeability. The experimental
values of the permeability coefficient are compared with those calculated by using a model taking into account the increased
path of diffusing water molecules caused by the shielding effect of plate like particles. The thermograms of differential
scanning calorimetry in the temperature range from −40 to 130°C are presented. The results of a thermogravimetric analysis
for specimens heated in air to 800°C are also reported.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 4, pp. 503–516, July–August, 2006. 相似文献
5.
R. D. Maksimov S. Gaidukovs M. Kalnins J. Zicans E. Plume 《Mechanics of Composite Materials》2006,42(2):163-172
A variant of stepwise determination of the elastic characteristics of quasi-isotropic polymer-silicate nanocomposites with
randomly oriented platelike filler particles is considered. First, the elastic constants of transversely isotropic structural
elements with coplanarly placed filler particles are obtained, and then they are averaged over all spatial directions by using
the orientational averaging method. The characteristic features of the hierarchical structure of exfoliated and intercalated
nanocomposites are also considered. The concentration dependences of elastic constants of a nanocomposite based on a styrene-acrylate
copolymer and native montmorillonite clay are modeled, and the results obtained are compared with experimental data.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 2, pp. 235–246, March–April, 2006. 相似文献
6.
Analysis results for the elastic properties of a composite with a small amount of coplanarly arranged platelike filler particles
are presented. The geometrical form of the particles is described by an oblate ellipsoid of revolution. The calculations are
performed by formulas obtained by using the Eshelby approach for media with a low concentration of inclusions. The effect
of anisometry of the ellipsoidal particles and of the ratio between the elastic moduli of the filler and matrix on the effective
elastic constants of the composite is discussed. Calculation results are compared with experimental data for the elastic moduli
of a nanocomposite containing completely exfoliated particles of an unmodified montmorillonite.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 493–504, July–August, 2008. 相似文献
7.
A variant of determining the elastic characteristics of composites containing irregularly oriented shape-anisotropic filler
particles of two types (short fibers and thin platelets) is considered. The effective elastic constants of the composites
are calculated by using the method of orientational averaging of elastic characteristics of isolated transversely isotropic
structural elements reinforced with unidirectionally oriented short fibers or coplanarly arranged thin platelets. The superposition
of elastic properties of the irregularly oriented structural elements, with account of their orientational distribution in
the composite material, is accepted. The calculation results are compared with experimental data for the effective elastic
moduli of polymeric composites reinforced with short glass fibers and of polymeric nanocomposites containing the platelet-type
particles of organically modified montmorillonite.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 3, pp. 285–300, May–June, 2006. 相似文献
8.
The Levenberg–Marquardt method is a regularized Gauss–Newton method for solving systems of nonlinear equations. If an error bound condition holds it is known that local quadratic convergence to a non-isolated solution can be achieved. This result was extended to constrained Levenberg–Marquardt methods for solving systems of equations subject to convex constraints. This paper presents a local convergence analysis for an inexact version of a constrained Levenberg–Marquardt method. It is shown that the best results known for the unconstrained case also hold for the constrained Levenberg–Marquardt method. Moreover, the influence of the regularization parameter on the level of inexactness and the convergence rate is described. The paper improves and unifies several existing results on the local convergence of Levenberg–Marquardt methods. 相似文献
9.
The stability of elastic columns subjected to axial pressure is studied. An elastic multistepped column with rectangular cross
sections are considered assuming that at the re-entrant corners of the column stable cracks are located. The influence of
a crack on the loss of stability of the column is described by means of local flexibility and the function of compliance coupled
with the stress intensity factor, which is known from the linear elastic fracture mechanics. A column with a single step is
studied in more detail. The influence of crack location and length on the buckling load is assessed numerically.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 87–100, January–February, 2006. 相似文献
10.
The influence of a preliminary bending induced by misalignment of the grips of a testing machine on the stress-strain state
of a flat specimen made of a high-strength unidirectional carbon fiber composite under uniaxial tension is estimated. An analysis
of the analytical solution obtained is carried out, and the results of finite-element calculations and modeling experiments
are presented.
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Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 6, pp. 745–760, November–December, 2007. 相似文献
11.
The propagation of flexural Lamb waves in a prestrained sandwich plate made from compressible highly elastic materials is
investigated within the scope of a piecewise homogeneous body model by utilizing TLTEWISB. The mechanical relations of layer
materials are described by a harmonic-type potential, and numerical results are obtained for the first and second vibration
modes. According to the results, the influence of problem parameters and of the initial stretching strain along the layers
on the wave propagation speed is examined. The asymptotic values of the speed are considered in the cases of short and long
wavelengths, and the influence of the initial strains on these asymptotic (limit) values are also analyzed.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 2, pp. 231–244, March–April, 2008. 相似文献
12.
V. P. Stavrov V. V. Stavrov N. V. Pankova K. Friedrich 《Mechanics of Composite Materials》2000,36(2):155-162
The influence of displacements of tensioned fibers on the impregnation of fibrous layers with a polymer melt and on the final
composite structure is studied. Using computer simulation, it is shown that, during impregnation, the structure of tensioned
fibrous layers changes considerably depending on the initial arrangement and tensioning of fibers. The consolidated regions
formed under the melt front move inside the impregnated layer with the advancing melt front. Displacement of the tensioned
fibers as well as the formation of “washouts” favors the impregnation of internal layers, but cause significant inhomogeneity
of the polymer structure. The surface (on the side of the melt flow) regions are more saturated with the polymer than the
internal ones. A difference in the melt percolation mechanisms at various impregnation regimes is revealed. The effective
permeability coefficients of a tensioned fiber layer are not constant but depend on the conditions and regimes of impregnation.
Submitted to the 11th Conference on the Mechanics of Composite Materials (Riga, June 11–15, 2000).
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 2, pp. 259–270, March–April, 2000. 相似文献
13.
LinFanMAO YanPeiLIU FengTIAN 《数学学报(英文版)》2005,21(2):225-236
A graph is called a semi-regular graph if its automorphism group action on its ordered pair of adjacent vertices is semi-regular. In this paper, a necessary and sufficient condition for an automorphism of the graph F to be an automorphism of a map with the underlying graph F is obtained. Using this result, all orientation-preserving automorphisms of maps on surfaces (orientable and non-orientable) or just orientable surfaces with a given underlying semi-regular graph F are determined. Formulas for the numbers of non-equivalent embeddings of this kind of graphs on surfaces (orientable, non-orientable or both) are established, and especially, the non-equivalent embeddings of circulant graphs of a prime order on orientable, non-orientable and general surfaces are enumerated. 相似文献
14.
An analytic solution of the thermal problem of friction for a plane-parallel layer–base tribosystem under conditions of incomplete
thermal contact between contacting bodies is obtained. Asymptotics of the obtained solution for small and large values of
time are determined. For the materials of a cermet layer–iron base friction pair, we investigate the influence of the thermal
conductivity coefficient of the contact on the temperature distribution and intensity of a heat fluxes. 相似文献
15.
In this work, the influence of initial stretching of a simply supported plate-strip containing two circular holes on the stress
concentration around the holes caused by bending of the strip is examined using the finite-element method. The mathematical
formulation of the corresponding boundary-value problem is presented within the frame work of the three-dimensional linearized
theory of elasticity (TDLTE) under a plane strain state. The material of the plate-strip is linearly elastic, homogeneous,
and orthotropic. The numerical results obtained in investigating the influence of the initial stretching and the location
of holes on the stress concentration are presented. In particular, it is established that the initial stretching significantly
decreases the stress concentration at some characteristic points on the contour of the holes.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 6, pp. 827–838, November–December, 2008. 相似文献
16.
István Deák 《Annals of Operations Research》2006,142(1):79-97
Two-stage models are frequently used when making decisions under the influence of randomness. The case of normally distributed
right hand side vector – with independent or correlated components – is treated here. The expected recourse function is computed
by an enhanced Monte Carlo integration technique. Successive regression approximation technique is used for computing the
optimal solution of the problem. Computational issues of the algorithm are discussed, improvements are proposed and numerical
results are presented for random right hand side and a random matrix in the second stage problems. 相似文献
17.
On the basis of a concept of complex characteristics, we present a statement of nonlinear conjugate problems of forced resonance
vibrations and dissipative heating of inelastic plates of physically nonlinear materials, for which the real and imaginary
parts of mechanical complex characteristics depend on the amplitude of deformations. Numerical-analytical methods for the
solution of the indicated nonlinear problems are presented. An analysis of the influence of physical nonlinearity on the amplitude–frequency
and temperature–frequency characteristics and on the coefficient of damping of vibrations of rectangular plates is performed. 相似文献
18.
To develop design rules for dynamically loaded composite structures, extensive static and cyclic tension/compression-torsion
tests were carried out on carbon-fibre-reinforced composites, in which especially the important influence of multiaxial loading
conditions on their fatigue behaviour was investigated. Physically based failure criteria for static loadings are modified
for multiaxial cyclic loadings, and a good agreement with experiments is achieved.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 5, pp. 631–641, September–October, 2006. 相似文献
19.
Yu. A. Gorbatkina 《Mechanics of Composite Materials》2000,36(3):169-176
The relationship between the strength (σc) of unidirectional fiber-reinforced plastics in different stressed states and the interfacial strength of their components
is investigated. The shear adhesive strength (τ0) of fiber—matrix joints determined by the pull-out technique is used as a measure of the interfacial strength. To obtain
the correlation curves betweenσc andτ0, the experimental results are used, where both the plastic and adhesive strength change under the influence of a single factor.
In this case, such factors are the fiber surface treatment, nature and composition of polymer matrices, and test temperature.
It is shown that the strength of the glass, carbon, and boron plastics increases practically linearly with increased interfacial
strength. Such a behavior is observed in any loading conditions (tension, shear, bending, and compression). Sometimes, a small
(10–20%) increase in the adhesive strength induces a significant (50–70%) growth in the material strength. Therefore, the
interface is the “weak link” in these composites. The shape of theσc—τ0 curves for composites based on the high-strength and high-modulus aramid fibers and different thermoreactive matrices depends
on the nature of the fiber and the type of stress state. In many cases, the composite strength does not depend on the interfacial
strength. Then, the fiber itself is the “weak link” in these composites.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000).
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 3, pp. 291–304, May–June, 2000. 相似文献
20.
We deal with the thermomechanical response of multilayer satin weave carbon-fiber-reinforced polymer (CFRP) laminates with
internal and/or edge cracks and temperature-dependent material properties subjected to tensile loading at cryogenic temperatures.
The composite material is assumed to be under the generalized plane strain. Cracks are located in the transverse fiber bundles
and extend to the interfaces between two fiber bundles. A finite-element model is employed to study the influence of residual
thermal stresses on the mechanical behavior of multilayer CFRP woven laminates with cracks. Numerical calculations are carried
out, and Young’s modulus and stress distributions near the crack tip are shown graphically.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 4, pp. 479–492, July–August, 2008. 相似文献